Distortion measurement circuit

ABSTRACT

A time distortion measurement circuit for use in conjunction with telegraphy apparatus wherein deviations from the theoretical time duration of steps corresponding to high speed telegraphic information transmission may be displayed on an oscilloscope. The distortion time, if any, of each telegraph information step is determined and stored so that a corresponding distortion indicating signal may be applied to the oscilloscope for a time interval equal to the time duration of the succeeding telegraph step. Thereby a distortion indicating signal of sufficient time duration to effect visual display of step time distortion is applied to the oscilloscope. Counting devices are employed that are responsive to a transition between successive steps and, more particularly, to a change in polarity of the applied telegraph signal, to produce control signals corresponding to their count that are stored and applied to the oscilloscope until the succeeding transition occurs. An indication of the actual time duration of the steps, and consequently of the percentage error between the actual time duration and the theoretical fixed time duration of the steps, is thereby obtained.

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[72] inventor Erwin Sehenk Primary Examiner-John W. Caldwell Munich, Germany Assistant ExaminerMarshall M. Curtis [21 Appl. No. 669,743 Attorney Birch, Swindler, McKie & Beckett [22] Filed Sept. 22, 1967 [45] Patented May 25, 1971 [73] Assignee Siemens Aktiengesellschaft Berlin, Germany [32] Priority Sept. 23, 1966 [33] Germany ABSTRACT: A time distortion measurement circuit for use in conjunction with telegraphy apparatus wherein deviations from the theoretical time duration of steps corresponding to high speed telegraphic information transmission may be displayed on an oscilloscope. The distortion time, if any, of each telegraph information step is determined and stored so that a [54] DISTORTION MEASUREMENT CIRCUIT corresponding distortion indicating signal may he applied to 5 claims 11 Drawing Figs the oscilloscope for a time interval equal to the time duration of the succeeding telegraph step. Thereby a distortion indicat- [52] US. Cl 178/69, ing signal of sufficient time duration to effect visual display of 340/324 step time distortion is applied to the oscilloscope Counting [5i] Int. Cl H04i 1/00 devices are employed that are responsive to 3 transition [50] Field Of Search 178/69 (A), between uccessive Steps and more particularly to a change 69 -1 28/ l 2; 340/167 324 in polarity of the applied telegraph signal, to produce control signals corresponding to their count that are stored and ap- [561 References C'ted plied to the oscilloscope until the succeeding transition oc- UNITED STATES PATENTS curs. An indication of the actual time duration of the steps,

2,856,457 l0/1958 Prior l78/69A and consequently of the percentage error between the actual 3,l29,286 4/1964 Levick l78/69A time duration and the theoretical fixed time duration of the 3,189,733 6/1965 Cannon 178/69A steps, is thereby obtained.

SYNCHRONlZATlON GENERATOR l.) DEWCE 3 f/ 1 ceuNTERi GEN l V TU Z1 Z2 l'='l- K3 2 A i l 5111 E v i MEASURING c itikit srv 511 F E5 ZT 61 K1 53 K2 H X y B E T A T V1 v3 (JSENZ [TI GENERATOR 2 a 2358 1 969" i t. -15? QR- PATENTED W25 I97! 3:5 1 09 SHEET 1 CF 3 Fig. 1 PRIOR ART V CONTROL l CIRCUI'F/ 51 K /HORIZONTAL SCANNING GENERATOR INPUT DEVICEy x CATHODE HORI'ZONTAL RAY TUBE DEFLECTION E5 CIRCUIT CIRCUIT PATEIIIEII IIII2 5187i SHEET 2 [IF 3 FIg.2 SYNCHRONIZATION GENERATOR I ,COUNTERS\ J G GENERATOR 2 I I a) M ES 5P GEN BINARY STORAGE DEV'CE I VERTICAL DEFLECTION DAU y CIRCUIT DIGITAL TO ANALOG CONVERTER CATHODE HORIZONTAL RAY- TUBE DEFLECTION CIRCUIT I I I I I I I I 2 I 3 I I. I 5 I slI bI I I I I I i I I I I l I I- C) I I I I I Ti I I I I I 2 d) I I I I I l BI /o IZ5/on U /o I 25 0% 50% I II. I I 25/ n w I2 I I I IV 00/ L I z (:3 I I l DISTORTION MEASUREMENT CIRCUIT REFERENCE TO PRIORITY APPLICATION Applicant claims priority from the corresponding German application Ser. No. Sl06,065, filed Sept. 23, 1966 in Germany.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to the measurement of distortion in the time duration of a signal, and in particular, to distortions in the time duration of telegraph signals transmitted at high step speeds, and the visual display of said distortions, ifany, on an oscilloscope. I

2. Description of the Prior Art The prior art teaches the utilization of telegraph distortion measurement apparatus employing an oscilloscope to indicate errors in the time duration of steps, for telegraph speeds corresponding to a maximum information transmission limit of 500 Ed. However, telegraph devices operating at this relatively low speed are no longer practicable for use in modern high speed data communication systems. If conventional means are used to measure the time distortion of steps and produce a corresponding control signal indicative of the transition between positive and negative polarities of the telegraph signal in conjunction with high rates of telegraph information transmission corresponding to approximately 5,000 Ed, the indicating signal produced is of insufficient time duration to produce a visual indication of the distortion value when it is applied to the oscilloscope.

Thus, in known telegraphy time distortion measurement apparatus employing a linear scale, the horizontal scanning period of the oscilloscope is selected to be equal to the theoretical time duration of a step. If it is desired to produce an accurate visual indication of termination of a particular telegraph step having a dissolution value 1 percent, a time period of approximately 0.25 to 0.50 percent of the theoretical step time interval is needed for recordation of the corresponding indicator signal. Recordation times less than this are insufficient to produce accurate visual indications of step termination; At telegraph step speeds corresponding to 5,000 Bd., this would correspond to an indicator signal time duration between 0.5 s to lps. However, an indicator signal of such short time duration is not sufficient to produce a visible indication on the oscilloscope screen.

SUMMARY OF THE INVENTION These and other defects of prior art apparatus are solved by the present invention, wherein means are employed to effectively prolong the time duration of indicating signals representative of transitions between successive steps, so that a visible display thereof can be produced by an oscilloscope when relatively high telegraph speeds approximately in the range 5,000 Bd. are used.

A synchronization generator is employed to produce pulses that are fed to a counting chain. When a transition between successive steps occurs, the count of the counting chain is transferred'to a binary storage device. A digital-analog converter is connected to the binary storage device, and is responsive to the count stored therein, to produce a corresponding voltage that is indicative of the relative distortion time of the last step, that is applied to the horizontal deflection circuit of the cathode-ray tube (CRT). When a count is transferred from the counting chain to the binary storage device, it is maintained therein until the succeeding transition between steps occurs. At that time, the succeeding count of the counting chain is transferred to the binary storage device, and controls the digital-analog converter to produce a corresponding voltage indicative if the new count, and therefore of the relative time at which the transition occurred.

A signal is also produced in response to transitions between successive steps, that is applied to the vertical deflection circuit, and which may be prolonged by excitation thereby of a generator, which produces a corresponding output that is applied to the vertical deflection circuit of the CRT. Thus, the invention effectively increases the time duration of indicating signals applied to the cathode-ray tube (CRT), that are responsive to transitions between successive steps, to time intervals that are sufficient to effect visible display of the transition on the oscilloscope screen. Corresponding scales may be employed for use in conjunction with the cathode-ray screen, to indicate the percentage distortion time of succeeding steps, depending upon the position of the visible indication produced on the cathode-ray screen, which, of course, is dependent upon the voltages applied to the horizontal and vertical deflection circuits associated therewith. The disclosed invention provides for increasing the time duration of a transition indication signal by a factor approximately within the range through 200.

Further, an additional advantage results, because the electron beam of the CRT is not moved during the time that a measurement of distortion time is being recorded, and this considerably increases the image quality of the resulting visible indications on the oscilloscope screen.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. la-1e illustrate the prior art, with FIG. 1a showing in block diagram form an example of the prior art distortion measurement apparatus, and graphs 1b1e serving to explain the operation thereof.

FIGS. 2a-2e illustrate the invention, with FIG. 2a showing in block diagram forman embodiment thereof, and graphs 2b- 2e serving to explain its operation. I

FIG. 3 is a circuit diagram of a distortion measurement apparatus according to the teachings of the invention, for use in a telegraph system.

DETAILED DESCRIPTION OF THE INVENTION FIG. la illustrates a prior art distortion measurement apparatus that employs a linear scale for the measurement of telegraph step signal time distortion. Thus, telegraph signalM is applied through input device ES to the measurement apparatus. It is then applied to the vertical deflection circuit (y) of cathode-ray tube B, hereinafter referred to as CRT B. Graph l b shows a typical series of successive telegraph signals having start step S, succeeded by a combination of five steps (1-5) representative of a particular code, and stop step St. The theoretical time duration of each of the five successive steps is equal to time period T.

Graph 10 shows the measuring cycle time duration, which commences with start step S and terminates with release of horizontal scanning generator K by control circuit ST; The measuring cycle time duration is set such that horizontal scanning generator K is deactivated, at a time equal to onehalf of the theoretical time duration (T/2) of an individual one of the steps l5, following entry of stop step St. The period of the scanning frequency of horizontal scanning generator K is equal to the theoretical step time duration T of telegraph signal M. Further, horizontal scanning generator K produces sawtooth wave signals as shown in graph 1e, which are applied to the horizontal deflection circuit (x) of CRT B.

Thus horizontal scanning generator K produces a sawtooth wave output after half of a start step entry signal S is applied to input device ES. Signals corresponding to the transition between positive and negative polarity steps are applied to the vertical deflection circuit (y) of CRT B, and produce successive indications thereof as illustrated in FIG; ldi

An appropriate scale may be used in conjunction with CRT B, wherein the relative position of the transition indication produced on theCRT screen may be used to indicate the percentage distortion of successive telegraph step signals. For example, with reference to FIG. 1e, it is seen that a transition indication will occur at a particular point during the horizontal deflection voltage applied to the horizontal deflection circuit of CRT B, and the corresponding visual impulse produced in the vertical direction will, therefore, occur at a particular point in the CRT screen and will depend upon the percentage distortion involved. Thus, the transition between steps 5 and l, for example (FIG. 11;), occurred exactly at the correct theoretical time, andthe vertical impulse will correspondingly be produced at the midpoint value of the horizontal deflection voltage, which may be made to correspond to the center of the CRT screen. Then, with reference to the transition between steps 1 and 2 wherein the transition occurs at a time 25 percent greater than theoretical time period T, the corresponding vertical indication pulse B will occur at a later point in the applied horizontal sawtooth deflection voltage. With reference to FIG. 1e, the corresponding visible impulse produced on the CRT screen will be to the right of the impulse produced at time A, and will correspond to positive 25 percent distortion voltage. Again, at time C, an impulse is produced at a point on the CRT screen that is coincident with the point at which the impulse producedat time A appears, because the time duration of step 2 corresponds to the theoretically correct value. Therefore, a percent distortion error is indicated. With reference to the transition between steps 4 and 5 at time D, it is seen that the transition occurred 25 percent of time period T prior to theoretical time period T that it should have occurred. Therefore, a corresponding vertical impulse is produced at time D during the horizontal scanning of the CRT screen within step 4, and this point is to the left of the 0 percent distortion indication point. Therefore, it may be made representative of a negative 25 percent time distortion error. Thus, with reference to FIGS. lb1e, it is seen that crrors within the positive range (0-50) percent, or the negative range (O50) percent may be indicated, utilizing the scale described with reference to the graph illustrated in FIG. 1e. Distortion indications in the negative range represent corresponding steps of time duration less than the theoretical time duration, and those in the positive range represent corresponding steps of time duration greater than the theoretical time duration.

If the indicator signal corresponding to a transition between steps is to have a theoretical dissolution value of l percent, it is necessary that the transition time and, hence, the recordation time be within the range of 0.25-0.50 percent of step time duration period T. Obviously, as the step time duration period T decreases, corresponding to faster rates of telegraph information transmission, as, for example, within the 5,000 Bd. range, the corresponding allowable recordation time corresponding to the theoretical dissolution value of 31 percent decreases to the point wherein the indicator signal produced, indicative of a transition between steps, is of insufficient time duration to effect visible display thereofon the CRT.

The invention illustrated in FIG. 2 provides an apparatus wherein the indication signal time duration is increased, relative to the prior art device illustrated in FIG. 1, when fast telegraphing speeds corresponding to approximately 5,000 Bd. are employed.

Thus with reference to FIG. 2, telegraph signal M is applied to input device ES. The vertical deflection circuit (y) of CRT B is connected to input device ES through generator 1. Also, a frequency stabilized synchronization generator T6 is connected to input device ES, and applies pulses of a predetermined frequency to counting chain meters Z1 and Z2.

The theoretical time period T of successive steps is divided into 100 units by meter Z1, which counts off the theoretical step period T. Thus, during each successive step, member Z1 counts to 100, with each hundredth count representing the termination of 'the theoretical time period T of the corresponding step. Counting claim meter Z2 determines the measuring cycle duration (see FIG. 1c), which, according to the illustrative example, lasts from the entry of start signal S to some point after stop signal St is entered. The distribution ratio of meter Z is commutatable depending upon the particular telegraph code being utilized to transmit the information.

It is seen that the telegraph signal shown in FIG. lb is time distorted in that the individual steps do not all terminate at the theoretically correct time. Further, assuming that the rate of telegraph signal transmission is within the range corresponding to 5,000 Ed, the prior art distortion measurement circuit discussed with relation to FIG. 1 may not be used successfully.

The telegraph steps have a theoretical time duration of period T, and may consist of a start step S, the five successive combination steps 1-5 corresponding to a particular code and indicative of specific information, and stop step St. The theoretical time duration of each of the five combination steps 11-5 is illustrated by the vertical broken lines in FIG. 2b. Further, the measuring cycle commences with entry of start step S, as shown in FIG. 2c. As discussed above, meter Z2 is set to determine the time duration of the measuring cycle according to the specific code being employed, and terminates the measuring cycle corresponding therewith; see FIG. 20.

Start step signal S is applied to generator TG through input device ES to cause activation thereof. Generator TG produces counting pulses that are fed to meter Z1, which produces exactly counting pulses during each of steps 15 of theoretical time period T. Meter Z1 is set to count I00 counting pulses, after which it automatically resets itself to the 0 position, and then again counts to 100. For distortion measurement purposes, the 100 possible count positions of meter Z] are assigned to corresponding distortion percentage values (-50 percent to +50 percent) of the actual time duration of steps relative to the theoretical time duration or period thereof, T.

Transitions between successive steps apply corresponding enabling signals to inquiry AND gate G that unblock it and cause the transfer of the count of meter Z1 to binary storage device SP. The meter count stored in binary storage device SP is converted by digital-analog converter DAU to a cor responding horizontal control signal, the polarity of which is dependent on whether the time duration of the corresponding step is more or less than the theoretical time duration T, and the amplitude of which is dependent upon the degree of deviation from the theoretical time (the distortion percentage), which is applied to the horizontal deflection circuit (x) of CRT B. Thus, the cathode ray or electron beam emission path of CRT B is maintained in a particular horizontal position for the time duration of the horizontal control signal corresponding to the time distortion of the completed step, relative to the center position corresponding to zero (0) time distortion.

When the next transition between steps occurs, inquiry AND gate G will again be enabled to transfer the corresponding count of meter Z1 binary storage device SP, which consequently causes a corresponding horizontal control signal to be produced by digital-analog converter DAU. The electron beam will then be repositioned, assuming that the time distortion of the corresponding step is different from that of the last step, to the corresponding position of the CRT screen, and will be maintained in that position for the time duration of the succeeding step. Thus, the time duration of a horizontal control pulse applied to the CRT to indicate the time distortion of a step, is equal to the time duration of the successive step, and is, therefore, applied to the CRT for a time interval that is sufflcient to enable visual display thereof on the CRT screen.

The setting of binary storage device SP and the corresponding horizontal control voltage produced by digital-analog converter DAU can be changed very quickly and, therefore, the apparatus is extremely sensitive to changes in the telegraph signal, and especially to transitions occurring between successive steps thereof.

The vertical deflections of the CRT are produced in response to activation of generator 1 in response to the transitions between successive steps. For example, generator 1 may comprise multivibrator means responsive to transitions between successive steps to produce corresponding vertical deflection voltages of sufficient time duration to produce visual indications of the percentage distortion at the CRT that are applied to the vertical deflection circuit (y) of the CRT. Further, the voltage amplitude produced by generator 1 may be varied depending upon the plurality of the telegraph signal M in order to recognize whether the distortion value obtained was derived from a step entry signal S of one or the other polarity. I

FIG. 2e shows the visual indications produced by the CRT during successive scanning periods of the CRT. Thus, it is seen that termination of step I occurred 25 percent of time period T, after which it should theoretically have occurred. Therefore, the corresponding count of meter Z1 is transferred by inquiry AND gate G to binary storage device SP at time B (see FIG. 2d) and produces a visible indication at a corresponding portion of the CRT screen for a time period equal to time II. The digital-analog converter DAU applies a voltage corresponding to the percentage distortion of step I to the horizontal deflection circuit (x) of CRT B until the successive transition that occurs at point C again enables gate G to transfer the count of meter Z1 to binary storage device SP. It is seen that step 2 terminates at the theoretically correct time, and therefore the count of meter Z1 corresponding to zero percentage distortion is transferred to binary storage device SP to control digital-analog converter DAU to produce a corresponding horizontal control signal that is applied to the horizontal deflection circuit (x), and which maintains the electron beam at the point in the CRT screen corresponding to the percentage distortion. Thus, it is seen with reference to FIG. 2e, that the horizontal deflection signal produced by digital-analog converter DAU applies a voltage corresponding to zero (0) percentage distortion during time t2, until point D, at which time another transition occurs between successive steps.

It is seen with reference to FIG. 2!; that step 4 terminates at a time, which is 25 percent of time period T, prior to the time it should theoretically terminate. Thus, inquiry AND gate G will be enable by the transition signal produced to transfer the corresponding count of meter Z1 to binary storage device SP. This will effect a corresponding horizontal control signal to be produced by digital-analog converter DAU that corresponds to a distortion percentage equal to negative 25 percent that is applied to the horizontal deflection circuit (x) of CRT B for time period t3, which terminates at point E (the transition between step 5 and clear signal St).

FIG. 3 illustrates a distortion measurement apparatus according to the invention employed in atelegraph system. The telegraph signal is applied to input E of flip-flop device ES, that may comprise a bistable multivibrator and associated output amplifier A having first and second stable conditions. The first stable condition corresponds to separation current condition T, and the second stable condition corresponds to signal current condition Z. Depending upon the polarity of the input signal applied to flip-flop device ES, a corresponding signal is thus produced either at output terminal T or Z thereof. When it is desired to measure distortions in the time duration between the entry of a start signal and the entry of a stop signal, switches SI, SH and SW are actuated to the position wherein their respective contacts are shown by the solid line contact positions.

Switch Sl functions to determine the time distortion to be measured. For example, in contact position 1, the time duration between the entry of start and stop is measured. In contact position 2, the synchronized alignment of the apparatus is measured, and in contact position 3, the step time duration distortion is determined.

Switch SII ascertains, when the time distortion between the entry of start and stop signals is being measured, whether the measuring cycles is to start with a step beginning with a separation signal current step T, or a signal current step Z. In

the position of step SII illustrated in FIG. 3, wherein the contact switch is connected to tenninal Z, the measuring cycle is initiated by a signal current step Z, that is, a start step of the telegraphy signal. If switch Sll is actuated such that its contact is connected to terminal T, the measuring cycle will be initiated with a separation current step T, that is, a stop step ST of the telegraphy signal.

Assuming, however, that the position of switch Sll is as shown in FIG. 3, the start step S of the telegraphy signal is applied to AND gate G4 through switch SII. The second input to AND gate G4 is connected to synchronization device TU, that synchronizes the pulses produced by generator G1, which may, for example, comprise a quartz generator. Thus, synchronization pulses are produced at the output of synchronization device TU. When a synchronization pulse is applied simultaneously with a start step S to AND gate G4, it is switched through and time cycle switch K3 is correspondingly activated to condition E. Time cycle switch K3 comprises flipflop means having a first stable condition A, and a second stable condition E. When it is activated to stable condition E, it produces a corresponding signal that activates bistable device K4, which increases the time duration of theleading edge of the applied start step S to a time interval corresponding to the time duration of two synchronization pulses produced at the output of synchronization device TU. The output of bistable device K4 is amplified by amplifier V2, and is then applied to the input of counting meters Z1 and Z2 through switch SI. The start signal S resets meters Z1 and Z2 to the zero (0) or rest position, and then releases meter Z1 and enables it to count the synchronization pulses produced at the output of synchronization device TU.

The time duration of the measuring cycle is set by measuring cycle device CS, which may be varied depending upon the code being utilized. In the present example, wherein a five step code is used, the number of theoretical steps selected is 6%, corresponding to start step S, the steps 1-5, and one-half of a stop step St (see FIG. 26). Of course, if other codesare employed, measuring cycle devices CS may be selectively varied to set the corresponding measuring time cycle. When counter 2 has counted 6% theoretical steps, measuring cycle device CS applies an input signal to gate G5, which functions to apply a corresponding signal to the input of AND gate G6 simultaneously with a synchronization pulse, to control AND gate G6 through, and produce a corresponding output signal therefrom that activates cycle switch K3 to condition A which terminates the measuring cycle.

During the measuring cycle, the pulses produced at the output of supervision device TU provide a constant enabling signal to control AND gates G1 and G2 through when separation current steps T and signal current steps Z, respectively, are applied thereto. Depending upon which of AND gates G1 or G2 are thus controlled through, flip-flop stage KI will be activated to produce a corresponding positive output signal. Thus, if a separation current step T is applied to input flip-flop device ES, AND gate G1 will be controlled through by the corresponding transition signal and flip-flop stage Kl will be activated to the condition wherein a positive pulse is produced at its T output. Similarly, if a signal current step Z is applied to input flip-flop device ES, AND gate G2 will be controlled through by the corresponding transition signal to activate flipflop stage Kl to the condition wherein a positive output signal is produced at its Z output.

The T and Z output sections of flip-flop stage K1 and the A output section time cycle switch are connected to logic gate G3. Logic gate G3 is blocked if time cycle switch K3 is in condition E (in response to a start step S) and either separation current steps T or signal current steps Z are applied to logic gate G3. However, if time cycle switch K3 is driven to condition A (in response to termination of the theoretically correct time interval between start and stop steps), and an output signal is reproduced at output T or Z of flip-flop stage K1 in response to a separation current step T or a signal current step Z, respectively, logic gate G3 will be unblocked and a positive signal corresponding to the transition will be produced at its output and applied to flip-flop stage K2. This is indicative of the fact that the actual time intervalbetween entry of start and stop steps of a telegraph signal is'longer than the theoretically correct time interval corresponding to the particular code employed. Flip-flop stage K2 is constantly enabled by the synchronization pulses produced at the output of supervision stage TU, and causes a corresponding control signal to be produced at its output, that is increased to the time duration to two synchronization pulses, and which is amplified by amplifier V1 and applied to AND gate G.

Further, if time cycle switch K3 is in condition E, indicating that the theoretically correct time interval between entry of start and stop steps have not yet elapsed, termination of the telegraph signal, such that neither signal current steps Z nor separation current steps T are produced, will cause AND gates G1 and G2 to be blocked, and consequently neither output T nor output Z of flip-flop stage K1 will produce output signals that block logic gate G3. Therefore, logic gate G3 will be con trolled through and corresponding output signals caused by the transition between successive steps will be applied therefrom to flip-flop stage K2. This in turn will cause flip-flop stage K2 to produce a corresponding control signal that is amplified by amplifier V1 and applied to AND gate G.

Therefore, an indication of the time at which a stop step St occurs produces a corresponding control signal at the output of flip-flop stage K2, that is applied to AND gate G to effect transfer of the count of Z1 to binary storage device SP as described above. The corresponding count is therefore indicative of the actual time interval between entry of start and stop polarity steps for particular telegraph signals, and causes a corresponding voltage to be applied by digital-analog converter to the horizontal deflection circuit (x) of CRT B. As explained with reference to FIG. 2, a corresponding scale can be employed to indicate the percentage time distortion.

1f switch S1 is actuated to position 2, the synchronization alignment distortion of the measurement apparatus shown in HQ 3 is measured. Thus, the start step circuit, comprising AND gate G4, time signal switch K3, bistable device K4, amplifier V2 and AND gate G6, is disconnected from the circuit shown in FIG. 3. Therefore, the leading edge of steps applied to input flip-flop ES, will synchronize AND gates G1 and G2 relative to the synchronization pulses produced at the output of synchronization stage TU. Further, meters Z1 and 22 will not be reset to zero in response to a start step, since the start step system is disconnected therefrom as described above. Thus, meters Z1 and Z2 are bypassed, and the alignment between the leading edges of the synchronization pulses and the signals corresponding to transitions between successive steps, relative to the synchronization pulses applied to flipflop K3, may be determined by the visual indication produced on the CRT B screen in conjunction with appropriate scales. Thus the percentage synchronization alignment with respect to time of the measurement system will be produced.

When switch S1 is in contact position 3, the measurement system shown functions to measure the time distortion of the time duration of telegraph steps. Thus, the start step system described above is again disconnected. However, meters Z1 and Z2 are responsive to the start step signal S applied to input E, which correspondingly produces a reset control signal to be applied to meters 21 and 22. Therefore, meters 21 and Z2 are responsive to a start step St, and are reset to zero (0) position thereby. Then, successive transitions between steps produce corresponding positive output voltages at the output of gate G3, which as described above are applied to AND gate G to transfer the corresponding count of meter Z1 to binary storage device SP. The remaining portion of the system functions similarly as described in relation to FIG. 2, with meter Z2 determining the measuring cycle for the telegraph signal, depending upon the particular cycle employed.

Digital-analog converter DAU is responsive to the signal stored in binary storage device SP to produce a corresponding horizontal deflection voltage that is amplified by amplifier V3 and applied to the horizontal deflection circuit (x) ofCRT B.

Counting pulses produced by counter Z] are also applied to brightness scanning device HT, which functions to control the electron beam such that the image it produces is extinguished following a time duration equal to 1% theoretical steps if, in the meantime, a transition between steps does not occur.

Further, the brightness scanning device HT is connected to the output of amplifier Vl, which functions to extinguish the electron beam during the time period it changes positions corresponding to successive step transitions. Therefore, a clear, well-focused indication of the time distortion error signals is produced.

An auxiliary generator G2 is provided to produce a signal applied to the vertical deflection circuit (y) of CRT over variable amplifier A B. The amplitude of the signal produced by variable amplifier A is determined by the amplitude of the telegraphy signals available at the output of flip-flop stage K1. Thus, depending upon whether flip-flop stage K1 is in condition T or Z, it will apply corresponding polarity signals to variable amplifier A, to effect the amplitude of the signal applied to the vertical deflection circuit (y) depending upon the corresponding transition (positive to negative or negative to positive). Further, the frequency of the signal produced by auxiliary generator G2 determines the time duration or period of the vertical deflection voltage, and therefore may increase it relative to the transition time duration. The voltage output of amplifier A is amplified by amplifier V4, and is then applied to the vertical deflection circuit (y). A linear scale, corresponding to that described in relation to FIG. 22, may be employed to determine the corresponding time distortion percentage.

When switch SlV is actuated to the closed position indicated by the broken line position thereof, the distortion measurement apparatus may be calibrated. Thus, different counts of meter Z1 are applied from free-running meter Z1 to input E, and a distortion reference scale may be produced on the screen of the CRT 13, whereby the distortion scale affixed thereto may be calibrated.

The distortion measurement apparatus functions at step speeds of approximately 5,000 Bd., and is shown as comprising a digital control circuit. However, an equivalent analog circuit may also be employed without departing from the teachings of the invention.

lclaim:

1. A measurement circuit for use in a telegraphy system having a source of telegraphy signals transmitted at a high rate of step speed to indicate on an oscilloscope with horizontal and vertical deflection circuits the time distortion of successive telegraphy steps caused by differences between the actual and theoretical time durations thereof, comprising:

a generator (TG, TU) to produce pulses having a predetermined repetition frequency, first counting means (Zl) connected to the generator to count the pulses produced therefrom, sad counting means having as many different digital counting positions as distortion values to be indicated and operating to count through all of said positions once during each projected step of said telegraphy signal, said first counting means further including means for resetting said counting means and causing same to count all of said positions in a cyclic manner each time, the last of said positions is reached,

second counting means (Z2) connected between said first counting means and said generator to count the number of counting cycles of said first counting means, said counting means being settable to a predetermined counting value and including means for deactivating said generator upon reaching said predetermined value thereby determining the duration of the measuring cycle of said apparatus,

means for receiving the telegraphy signal to be measured,

storage means (SP) for digitally storing a digital signal representative of the counted value in said first counting means,

control means (G) responsive to transitions between successive steps of said telegraphy signal at said receiving means to cause, simultaneously with each of said transitions, transfer of the instantaneous counted value in said first counter to said storage means,

converter means (DAU) for receiving said stored digital signal from said storage means, for converting same to an analog signal corresponding thereto, and for applying said analog signal 'to one of said deflection circuits, said converter means maintaining said analog signal on said one deflection circuit until said storage means receives a signal indicative of a succeeding step of said telegraphy signal, and

a source of alternating voltage coupled to the other of said deflection circuits for applying an alternating voltage thereto responsive to a step transition at said receiving means.

2. The apparatus defined in claim 1 comprising in addition modulating means (A) for controlling the amplitude of said alternating voltage responsive to the polarity of said telegraphy signal causing said alternating voltage to have a different predetermined amplitude for each polarity of said telegraphy signal.

3. The measurement circuits recited in claim 2, further comprising a brightness scanning device (HT) connected between the first counting means and the oscilloscope to extinguish the electron beam associated with the oscilloscope during the time that the count of said first counting means is being transferred to the storage means said first counting means further including means for applying a signal to said brightness device to extinguishing said electron beam after a predetermined time duration after the transfer of a value from said first counting means to said storage means.

4. The measurement circuit recited in claim 3 wherein the brightness scanning device (HT) is further connected to the control means (G, K2) to cause the electron beam associated with the oscilloscope to be extinguished when a transition between successive steps does not occur for a predetermined time interval.

5. A measurement circuit as recited in claim 4 wherein the brightness scanning device is further operative to activate an extinguished electron beam in response to another step signal being applied to the measurement circuit. 

1. A measurement circuit for use in a telegraphy system having a source of telegraphy signals transmitted at a high rate of step speed to indicate on an oscilloscope with horizontal and vertical deflection circuits the time distortion of successive telegraphy steps caused by differences between the actual and theoretical time durations thereof, comprising: a generator (TG, TU) to produce pulses having a predetermined repetition frequency, first counting means (Z1) connected to the generator to count the pulses produced therefrom, sad counting means having as many different digital counting positions as distortion values to be indicated and operating to count through all of said positions once during each projected step of said telegraphy signal, said first counting means further including means for resetting said counting means and causing same to count all of said positions in a cyclic manner each time, the last of said positions is reached, second counting means (Z2) connected between said first counting means and said generator to count the number of counting cycles of said first counting means, said counting means being settable to a predetermined counting value and including means for deactivating said generator upon reaching said predetermined value thereby determining the duration of the measuring cycle of said apparatuS, means for receiving the telegraphy signal to be measured, storage means (SP) for digitally storing a digital signal representative of the counted value in said first counting means, control means (G) responsive to transitions between successive steps of said telegraphy signal at said receiving means to cause, simultaneously with each of said transitions, transfer of the instantaneous counted value in said first counter to said storage means, converter means (DAU) for receiving said stored digital signal from said storage means, for converting same to an analog signal corresponding thereto, and for applying said analog signal to one of said deflection circuits, said converter means maintaining said analog signal on said one deflection circuit until said storage means receives a signal indicative of a succeeding step of said telegraphy signal, and a source of alternating voltage coupled to the other of said deflection circuits for applying an alternating voltage thereto responsive to a step transition at said receiving means.
 2. The apparatus defined in claim 1 comprising in addition modulating means (A) for controlling the amplitude of said alternating voltage responsive to the polarity of said telegraphy signal causing said alternating voltage to have a different predetermined amplitude for each polarity of said telegraphy signal.
 3. The measurement circuits recited in claim 2, further comprising a brightness scanning device (HT) connected between the first counting means and the oscilloscope to extinguish the electron beam associated with the oscilloscope during the time that the count of said first counting means is being transferred to the storage means said first counting means further including means for applying a signal to said brightness device to extinguishing said electron beam after a predetermined time duration after the transfer of a value from said first counting means to said storage means.
 4. The measurement circuit recited in claim 3 wherein the brightness scanning device (HT) is further connected to the control means (G, K2) to cause the electron beam associated with the oscilloscope to be extinguished when a transition between successive steps does not occur for a predetermined time interval.
 5. A measurement circuit as recited in claim 4 wherein the brightness scanning device is further operative to activate an extinguished electron beam in response to another step signal being applied to the measurement circuit. 